Metallic recuperator and method of operating same

ABSTRACT

A metallic recuperator structure comprising one or more recuperators each comprising an annular chamber defined by an inner cylinder and an outer cylinder surrounding the inner cylinder, a heat absorbing medium being forcibly drawn through the annular chamber while the heating medium passes through the inner cylinder.

United States Patent 1191 Mar. 19, 1974 .1 acobs METALLIC RECUPERATOR AND METHOD 3,529,812 9/1970 Wunning 263/20 x 01: OPERATING SAME 3,l 17,539 1/1964 Heyn 1 263/20 X 1,714,893 5/1929 Smith 122/4 R [75] Inventor: Heinz Ja l rn, rm y 3,446,279 5/1969 White et al. 263/20 x 1,928,600 9/l933 Morton 1 263/20 [73] Assgnee' fi r g g 3,l80.407 4/1965 Hanke 263/20 x m 1 re e1 1 ermany 2,917,285 12/1959 Schack 263/20 x [22] Filed: Jan. 26, 1972 [21] Appl. No: 220,835 Primary Examiner-Manuel A. Antonakas Attorney, Agent, or Firm-Walter Becker [30] Foreign Application Priority Data Feb. 1, 1971 Germany 2104532 [5 ABSTRACT [52] Us. Cl 165/1 432/176 A metallic recuperator structure comprising one or [51] Int Cl 2 15/04 more recuperators each comprising an annular cham- {581 Fie'ld 263/20 ber defined by an inner cylinder and an outer cylinder 363/19 surrounding the inner cylinder, a heat absorbing medium being forcibly drawn through the annular cham- [56] References Cited ber while the heating medium passes through the inner l' d UNITED STATES PATENTS Cy m er 2,749.1 l0 6/1956 Hartwig 263/20 6 Claims, 4 Drawing Figures The present invention relates to a metallic recupera tor which comprises an inner cylinder through which the heating medium is flowing and an outer cylinder coaxially surrounding the inner cylinder, while the heat absorbing medium is passing through the space between the inner and the outer cylinder.

Metallic recuperators of this type are known. For determining the wall thickness of the hot inner cylinder, the outer overpressure of the heat absorbing medium as well as the temperature of the respective material and the characterizing strength values and the elasticity modulus are of importance. The wall thickness derived from these values furnishes a sufficient service life provided that the temperatures of the materials are the same at all places. This requirement is met when the untrue or non-circular factor is less than 1.5. This factor can with large diameters and relatively thin wall thicknesses be maintained only under great difficulties in production technical respect, and very slight at first hardly controllable deviations will become larger during the operation of the recuperator. The different wall temperatures resulting therefrom will, when the recuperator is in operation, bring about a local overheating of the material which overheating together with the pressure of the medium to be heated, which pressure acts upon the inner cylinder, leads to the well known buckling or bulging effects and destructions.

Greater wall thicknesses would counteract these drawbacks. An increasing wall thickness, however, will in view of the increasing resistance against the passage of heat cause widely differing temperatures of the material between the inner phase and the outer phase of the inner cylinder, whereby heattensions occur in the material which in the course of time will become higher than twice the permissible elastic limit. In addition thereto, due to the turning-on and turning-off and due to differing loads with respect to quantity, pressure and temperature, a fatigue of the material will result in view of the occurring different loads.

it is, therefore, an object of the present invention to provide a recuperator of the above described general character, which will make it possible to produce the inner cylinder of a thin-walled material without encountering the above referred to drawback of buckling or bulging, in other words without the danger that radially inwardly directed bulges or elevations on the inside of the inner cylinder will occur.

This object and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 illustrates a recuperator according to the present invention in which the heat absorbing medium is drawn through the recuperator in counter-current to the heating medium.

FIG. 2 illustrates a recuperator according to the invention in which the heat absorbing medium and the heating medium are passed through the recuperator in uni-directional flow.

FIG. 3 represents a recuperator according to the invention which is composed of two individual recuperators arranged in series one behind the other with regard to the heat absorbing medium.

FIG. 4 illustrates a recuperator according to the invention which is composed of two individual recuperators arranged in parallel to each other with regard to the heat absorbing medium.

The metallic recuperator according to the present invention which comprises an inner cylinder passed through by the heating medium and an outer cylinder coaxially surrounding the inner cylinder while the heat absorbing medium passes through the space between the two cylinders, is characterized primarily in that the heat absorbing medium is drawn through the space between the two cylinders.

The present invention is based on the general idea, in contrast to the heretofore customary construction and known use of metallic recuperators with two cylinders concentrically arranged one within the other, not to press the heat absorbing medium through the recuperator, whereby the above described drawbacks of heretofore known recuperators are created, but to draw the heat absorbing medium through the intermediate space between the two cylinders.

The heat absorbing medium is, in conformity with a further development of the invention, drawn through the intermediate space or chamber between the cylinders at an underpressure of a maximum of 1,000 water column. As a result thereof, the further advantage of the present invention is realized, namely a lower pressure difference with regard to the atmosphere in the intermediate space between the two cylinders.

According to a further advantageous development of the invention, the outer cylinder has a plurality of small openings distributed over its height and its circumference, which openings are adapted selectively to be opened. By opening these small openings, atmospheric air can reach the areas to be cooled of the inner cylinder. To this end, it is not necessary to press-in atmospheric air by special blower means or through blower conduits, but it will suffice to open the small openings in a corresponding manner in order to obtain a cooling of the desired areas of the inner cylinder.

According to a still further development of the invention, the intermediate chamber for the heat absorbing medium leads at its one end into an annular chamber known per se and has its other end with its full cross section in communication with the outer atmosphere.

The present invention furthermore comprises a metallic recuperator which is composed of a plurality of individual recuperators each of which has the above described features. In this connection, the individual recuperators are with regard to the heat absorbing medium and while employing a suction device arranged serially or parallel with regard to each other.

When arranging the individual cylinders parallel to each other, according to a further feature of the invention, the recuperators are provided with two annular chambers at the ends of the intermediate space between the cylinders. That annular chamber which is provided with the inlet opening for the heat absorbing medium is equipped with an adjustable flap, or the opening itself is equipped with an adjustable flap. By means of this flap it is possible to vary the ratio of the quantities of the heat absorbing mediae which are drawn through the individual recuperators.

Referring now to the drawings in detail, the recuperator according to the invention as illustrated in FlG. 1 comprises an inner cylinder 3 and an outer cylinder 2 coaxially surrounding the inner cylinder 1. Between the inner and outer cylinders there is formed an intermediate space or chamber 3 which has an annular cross section. The lower end 3a of the intermediate chamber 3 leads into a lower annular chamber 1 the upper flange 5 of which is tightly connected to the outer cylinder 2, while the end 20 of the outer cylinder 2 leads into the lower section of the annular chamber 4. The annular chamber 4 communicates with a suction device 6 which withdraws the heated up medium from the annular chamber 4 in the direction of the arrow 7 and thus withdraws the heated up medium from the intermediate chamber 3.

The heat absorbing medium flows in the direction of the arrow K into the intermediate chamber 3 between the two cylinders 1, 2 and passes in the direction of the arrow F to the annular chamber 4. Whereas the lower end of the recuperator is provided with the above described annular chamber 4, the intermediate chamber 3 at the upper end of the recuperator with its entire cross section leads at 8 into the outer atmosphere. This means that at the inlet end of the heat absorbing medium' into the intermediate chamber 3 no annular chamber is necessary.

According to the embodiment of FIG. 1, the heating medium is by means of the suction device 6 drawn through the cylinder 1 in the direction of the arrow 9 and thus in counter-current to the medium flowing in the intermediate space or chamber 3. The heat absorbing medium flows through the intermediate chamber at a sub-atmospheric pressure of up to 500 water column.

The embodiment illustrated in FIG. 2 corresponds to that of FIG. 1 with the exception that the upper end of the recuperator is equipped with an annular chamber 10 which is of the same or similar design as the annular chamber 4 of FIG. 1 and which has connected thereto a suction device 11 for withdrawing the heated up medium through the intermediate chamber 3 in the direction of the arrow S. Correspondingly, the lower end of the annular chamber 3 leads with full cross section into the outer atmosphere where the air to be heated up is drawn in in the direction of the arrow W.

The inner cylinder 1 can be thin-walled because no overpressure prevails in the intermediate chamber 3 which could bring about an inward buckling or bulging of the inner cylinder. Such buckling or bulging is indicated in FIGS. 1 and 2 by dash lines designated with the reference numeral 12 and will occur when the inner cylinder is thin-walled and the heat-absorbing medium is passed at an overpressure through the annular chamber 3.

According to the embodiment illustrated in FIG. 3, the two individual recuperators 1.3, 14 are arranged in series with regard to the heat absorbing medium. The upper individual recuperator corresponds as to its design to the recuperator of FIG. 1 and is equipped with the annular chamber 4 which through a conduit 115 communicates with the lower annular chamber 16 of the individual recuperator 14. The design of the recuperator 14 is similar to that of FIG. 1 and to that of the recuperator 13 of FIG. 3. However, the recuperator 14 has its upper end equipped with a second annular chamber 17 into which the intermediate space or chamber 3 of the recuperator 14 leads. From this annular chamber 17, the heat absorbing medium is by means of a suction device 13 drawn from the two serially arranged individual recuperators. While the heating medium flows in the individual recuperator 13 in countercurrent to the heat absorbing medium, the heating medium flows in the recuperator 14 in uni-directional flow with regard to the heat absorbing medium.

With the embodiment illustrated in FIG. 4, the recuperator likewise comprises two individual recuperators 19, 20 of which the upper recuperator 19 corresponds to the recuperator of FIG. 1. The annular chamber 21 of the recuperator 19 communicates through a conduit 22 with the suction device 23. The lower individual re cuperator 21 either has the same design as the upper recuperator (with the difference that it is shorter) or each of its upper and lower ends is equipped with an annular chamber 24, 25 respectively. The medium to be heated for the recuperator 211 enters the annular chamber 2 1, and the heated up medium is by means of the suction device 23 withdrawn from the annular chamber 25 through the conduit 26. The annular chamber 24 itself or the inlet opening to the chamber 241 may be provided with a flap or valve 27. By means of this flap or valve 27 it is possible to vary the ratio of the heat absorbing medium in the recuperators 19 and 20. Thus, for instance, when the flap or valve 27 occupies one position, 30 percent of the heat absorbing medium withdrawn by the suction device 22 may be passed through the recuperator, whereas percent of the heat absorbing medium is passed through the upper recuperator. In another position of the flap or valve 27, 40 percent of the heat absorbing medium may be passed through the lower recuperator, and 60 percent of the heat absorbing medium may be withdrawn through the upper recuperator.

The recuperators illustrated in FIGS. 14 have distributed over their circumference and over the height of the recuperator small openings with flaps orvalves 28 through which when opened cold air can pass to the inner cylinder 1. By selectively opening and closing these flaps or valves, it is possible by means of the inflowing fresh air to vary the surface temperature at those areas of the inner cylinder 1 which are endangered by excessive heat. These valves 28 are shown in FIGS. 1 and 2 only but preferably are also present in the designs of FIGS. 3 and 4. Moreover, while FIGS. 1 and 2 show only the lower portion of the outer cylinder 3 provided with valves or controllable openings 28 adapted selectively to be opened and closed, it is to be understood that the valves or openings 2% may be distributed over the entire length and also over the circumference of the outer cylinder.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings but also comprises any modifications within the scope of the appended claims.

What I claim is:

1.. A metallic recuperator to effect heat exchange between two different mediums, which includes in combination an inner cylinder adapted to be passed through by a heat-releasing medium, an outer cylinder substantially coaxial with and surrounding said inner cylinder so as to form therewith an intermediate annular chamber, and means communicating with said annular chamber for drawing a heat absorbing medium that flows through said intermediate annular chamber and that is basically different from the heat-releasing medium both as to temperature of the mediums being different and also being different as to composition and flow speed thereof, said outer cylinder having opening means distributed over its length and circumference and adapted selectively to be opened and closed for regulating the temperature of said inner cylinder.

2. A metallic recuperator in combination according to claim 1, which includes chamber means arranged at and communicating with one end of said annular chambet, the other end of said annular chamber communicating over its entire cross section with the atmosphere.

3. A metallic recuperator in combination according to claim 1, which includes a plurality of recuperators each having an annular chamber; and suction means communicating with said annular chambers for drawing said heat absorbing medium admitted into said annular chambers through the same.

4. A metallic recuperator in combination according to claim 3, in which the annular chambers of said recuperators are arranged in series with regard to each other.

' 5. A metallic recuperator in combination according to claim 3, in which the annular chambers of said recuperators are arranged in parallel with regard to each other.

6. A metallic recuperator in combination according to claim 3, which includes chamber means at each end portion of the annular chamber of one of said recuperators, that one of said chamber means which is adjacent to the inlet means of the pertaining annular chamber having associated therewith adjustable valve means for selectively controlling the heat absorbing medium entering said last mentioned annular chamber. 

1. A metallic recuperator to effect heat exchange between two different mediums, which includes in combination an inner cylinder adapted to be passed through by a heat-releasing medium, an outer cylinder substantially coaxial with and surrounding said inner cylinder so as to form therewith an intermediate annular chamber, and means communicating with said annular chamber for drawing a heat absorbing medium that flows through said intermediate annular chamber and that is basically different from the heat-releasing medium both as to temperature of the mediums being different and also being different as to composition and flow speed thereof, said outer cylinder having opening means distributed over its length and circumference and adapted selectively to be opened and closed for regulating the temperature of said inner cylinder.
 2. A metallic recuperator in combination according to claim 1, which includes chamber means arranged at and communicating with one end of said annular chamber, the other end of said annular chamber communicating over its entire cross section with the atmosphere.
 3. A metallic recuperator in combination according to claim 1, which includes a plurality of recuperators each having an annular chamber; and suction means communicating with said annular chambers for drawing said heat absorbing medium admitted into said annular chambers through the same.
 4. A metallic recuperator in combination according to claim 3, in which the annular chambers of said recuperators are arranged in series with regard to each other.
 5. A metallic recuperator in combination according to claim 3, in which the annular chambers of said recuperators are arranged in parallel with regard to each other.
 6. A metallic recuperator in combination according to claim 3, which includes chamber means at each end portion of the annular chamber of one of said recuperators, that one of said chamber means which is adjacent to the inlet means of the pertaining annular chamber having associated therewith adjustable valve mEans for selectively controlling the heat absorbing medium entering said last mentioned annular chamber. 